I know that when people get older, their body physics often change. For example, growing hair where we don't have hair, or not growing hair where we once had hair. And, what about with people gaining weight as they get older. As men age, and begin producing less and less testosterone, the length of their penis erections often shrink. Issac Newton's Laws of Physics, one of which says
"for every action, there is a equal reaction". So, I wouldn't say there is no way to grow the penis, as there probably is ... certainly if the body can chemically change to cause the penis to shrink, it can also be changed to grow the penis.
Years ago I scientifically tried the Extenze product, using it every day for 3 months, and taking measurements every week, and I can say that product SUX'd ! Didn't do a darn thing, plus, when I returned the product to get a refund, I never received the refund.